1. Field of the Invention
The present invention relates to the field of micro-injecting devices and ink jet print heads, particularly to membrane-type micro-injecting devices, and more particularly to the method of filling these devices with working fluid.
2. Description of the Related Art
Generally, a micro-injecting device refers to a device which is designed to provide printing paper, a human body or motor vehicles with a predetermined amount of liquid, for example, ink, injection liquid or petroleum using the method in which a predetermined amount of electric or thermal energy is applied to the above-mentioned liquid, yielding a volumetric transformation of the liquid. This method allows the application of a small quantity of a liquid to a specific object.
Recently, developments in electrical and electronic technology have enabled rapid development of such micro-injecting devices. Thus, micro-injecting devices are being widely used in daily life. One example of the use of micro-injecting devices in daily life is the inkjet printer.
The inkjet printer is a form of micro-injecting device which differs from conventional dot printers in the capability of performing print jobs in various colors by using cartridges. Additional advantages of inkjet printers over dot printers are lower noise and enhanced quality of printing. For these reasons, inkjet printers are gaining immensely in popularity.
An inkjet printer generally includes a printer head having nozzles with a minute diameter. In such an inkjet printhead, the ink which is initially in the liquid state is transformed and expanded to a bubble state by turning on or off an electric signal applied from an external device. Then, the ink so bubbled is injected so as to perform a print job on a printing paper.
Many methods and apparatuses for injecting working liquid are disclosed. In one type of micro-injection device, the printing operation on printing paper is executed using the vibration of a membrane, to drive the ink. In this type of device, a working liquid having the property of readily generating vapor pressure fills a heating chamber and induces the vibration. An example of this type of printhead is seen in U.S. Pat. No. 4,480,259, to Kruger et al., entitled Ink Jet Printer With Bubble Driven Flexible Membrane.
In a conventional method of filling such an inkjet printhead with working fluid, to continuously supply the working liquid into the inner portion of the heating chamber, a working liquid injecting device is installed on a portion of a cartridge, another portion of which is adjacent to the ink-jet printhead. Thus, the cartridge is attached to the inkjet printhead and the cartridge is filled with ink in the inner portion.
A method for injecting working liquid by using the working liquid injecting device will be now be described in detail. The working liquid stored in a working liquid reservoir is rapidly injected into the inkjet printhead according to a predetermined pressure applied by a pressurizing device (not shown). Then, the working liquid flows via a working liquid supply pipe into a working liquid supply channel through a supply hole and fills each heating chamber. In the mean time, the working liquid which remains after filling each heating chamber through the above-mentioned process is returned to a working liquid return unit via a working liquid return pipe. Then, the working liquid injection is finished by sealing the heating chambers.
However, the above-mentioned conventional method for injecting working liquid into the inkjet printhead has some problems. For the purpose of injecting the working liquid into each heating chamber, the separate and additional working liquid injecting devices are installed on the cartridge and the working liquid is injected into the separate inkjet printhead by using the separate working liquid injecting devices. Accordingly, total manufacturing time for manufacturing products increases and total manufacturing processes are complicated. Moreover, the total production yield decreases according to the complexity of manufacturing processes.
Examples of contemporary techniques for filling liquids in devices and moulds are seen in the following U.S. Patents. U.S. Pat. No. 5,601,125, to Parsoneault et al., entitled Vacuum Fill Technique For Hydrodynamic Bearing, describes a method for filling a hydrodynamic bearing with oil. U.S. Pat. No. 5,335,711 to Paine, entitled Process And Apparatus For Metal Casting, describes a process for casting molten metal into a mould involving subjecting the poured metal in the mould to pressure to reduce the porosity of the cast product. However, these techniques are not directly applicable to micro-injection devices.